The regulation of "cyclic 3', 5'-nucleotide phosphodiesterase" will be investigated utilizing a Ca to the 2nd power ion-dependent phosphodiesterase from brain as a model system. Stabilizing substances are sought to protect the enzyme at high degrees of purification. Interactions among "Ca to the second power ion", a "Ca to the 2nd power ion-dependent regulator" protein (CDR), and the phosphodiesterase will be investigated by circular dichroic spectrophotometry utilizing lysophosphatidyl choline as an alternate activator. The subunit composition of the enzyme will be determined by SDS analytical gel electrophoresis and the molar ratio of CDR required for the activation of one mole of enzyme determined. Antibodies will be prepared against the enzyme. Relationships between the Ca to the 2nd power-dependent phosphodiesterase of brain and membrane bound forms of cyclic nucleotide phosphodiesterase will be sought through the techniques of enzyme purification, kinetic and physical characterization, and cross reactivity with antibody to the Ca to the 2nd power-dependent phosphodiesterase. An observed dependence on CDR by a "Ca to the 2nd power-dependent adenylate cyclase" from brain will be evaluated for relationships with the CDR-dependent adenylate cyclase. Various cloned lines of glioma and neuroblastoma will be tested for the presence of CDR-dependent phosphodiesterase, and the CDR-dependent adenylate cyclase. The influence of various drugs, such as the phenothiazines, will be tested on these enzyme activities in tissue culture. BIBLIOGRAPHIC REFERENCES: Brostrom, Charles O., Huang, Y.-C., Breckenridge, Bruce McL., Wolff, D.J., Identification of a calcium-dependent regulator of brain adenylate cyclase. Proc. Natl. Acad. Sci. U.S.A., "72", 64 (1975). Huang, Y.-C., Wolff, D.J., Brostrom, C.O., Properties of a brain adenylate cyclase activity regulated by a Ca to the 2nd power ion-binding protein. Fed. Proc., "34", 617 (1975).